Get external references (cross-references) for a gene
AI agents call get_xrefs_by_gene to retrieve information from Ensembl MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves reference data linking genes to external databases. It performs a read-only query operation with no capability to modify, delete, or execute code. The blast radius of misuse is minimal—an agent could only retrieve cross-reference information that is already publicly available through the Ensembl API. There are no destructive, financial, or execution consequences from calling this tool.
From the tool's definition Tool name contains 'get_' verb and description states 'Get external references (cross-references) for a gene', indicating data retrieval with no modification or side effects.
Attacks that exploit this kind of access
Get external references (cross-references) for a gene. It is categorised as a Read tool in the Ensembl MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Ensembl MCP Server MCP server in PolicyLayer and add a rule for get_xrefs_by_gene: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Ensembl MCP Server. Nothing to install.
get_xrefs_by_gene is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the get_xrefs_by_gene rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for get_xrefs_by_gene. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
get_xrefs_by_gene is provided by the Ensembl MCP Server MCP server (munch-group/ensembl-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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